RealView: Add debug-macro.S support for the PB1176 platform

The UART0 address is different on PB1176 from EB or PB11MPCore. This
patch adds the necessary #ifdef's to this file. The disadvantage is
that enabling CONFIG_DEBUG_LL will work properly on PB1176 if only
this platform is enabled.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>